The thinnest single-mode optical fiber

The thinnest commercially available single-mode optical fibers have an overall diameter of 200 µm with a core diameter around 8–9 µm.Standard Single-Mode Fibers

Typical single-mode fibers, such as the widely used SMF-28, have a core diameter of approximately 8.2 µm and a mode field diameter of about 9.2 µm at 1310 nm or 10.4 µm at 1550 nm, with a cladding diameter of 125 µm and an overall fiber diameter including coating around 242 µm . These fibers are compliant with ITU-T G.652.D standards and are optimized for long-haul and high-speed data transmission .

Ultra-Thin Single-Mode Fibers

For applications requiring smaller, lighter, high-fiber-count cables, Corning offers SMF-28 Ultra fibers with a reduced overall diameter of 200 µm while maintaining the standard 9.2 µm mode field diameter . These fibers retain excellent attenuation and bend performance, exceeding ITU-T G.657.A1 recommendations, making them suitable for dense cabling environments such as data centers and FTTH deployments.

Specialized Single-Mode Fibers

Other ultra-thin fibers, such as Thorlabs' SM300, SM400, and S405-XP fibers, feature pure silica cores with fluorine-doped cladding and can operate across a wide wavelength range (320–2200 nm). These fibers are designed for high power handling and reduced photodarkening, with core diameters typically in the 8–10 µm range and overall diameters slightly larger than 200 µm depending on coating . They are particularly used in laboratory, sensing, and specialized optical systems.

Summary

• Core diameter: ~8–9 µm
• Mode field diameter: ~9.2 µm at 1310 nm
• Cladding diameter: 125 µm
• Overall fiber diameter (coated): 200–242 µm for ultra-thin fibers The 200 µm SMF-28 Ultra fiber represents the thinnest widely available single-mode optical fiber suitable for commercial and high-density applications, combining minimal size with excellent optical performance .